I have a pair of AV123 X-LS classics powered by a t-amp and a pair of Swan M200 MKII.
They're both good. I haven't had both in the same place to do any real testing though. I'd have a hard time picking which one I like better based on what I know now.
I guess with powered monitors, you're getting a set that's geared toward near field listening, and something that has amplifier capabilities matched to the speaker.
With bookshelf speakers, you have more options for expanding the system later on (by getting an amp with subwoofer output, hooking up the passive speakers to a receiver, etc.)
You'll have more options since you can basically do any combo you want.
Either way you want to do it will work.
I mainly did the T-amp and bookshelf combo for my office system since Kaido gave me the t-amp as a gift.
I bought a pair of b-stock speakers to go with them, and a power supply to power the t-amp since it wasn't included with the amp at the time.
All together I think the system was probably $250 worth of stuff.
The M200 MKIIs I bought for my sister, but she moved to England for a year (as of 2 days ago) and gave the Swans back to me. I've been using them at home while I get my main system sorted out (as I described in the massive DIY room treatments thread I started tonight).
I'm happy with the results of both systems.